The disclosed air-conditioning system for a vehicle driven by a motor, has a refrigerant circuit with a plurality of heat exchangers through which a refrigerant can be conducted for an exchange of heat with the air which flows through them, and has a heat pump heat exchanger in which an exchange of heat with a coolant circuit, in which at least one coolant cooler is arranged, takes place. It is possible for the coolant cooler, in the heating mode, to be used as a heat exchanger for absorbing heat from the environment. It is possible for the coolant cooler to be connected in series downstream of the heat pump heat exchanger in the coolant circuit A method for regulating such an air-conditioning system is also disclosed.